Retaining nut



FIG. 1 is a front perspective view of a retaining nut showing our new design;

FIG. 2 is a right side view thereof, the left side being a mirror image;

FIG. 3 is a top view thereof, the bottom being a mirror image;

FIG. 4 is a front view thereof; and

FIG. 5 is a rear view thereof. 

The ornamental design for a retaining nut, substantially as shown. 